1. Field of the Invention
The present invention relates to wooden trusses used for supporting structural loads and to hardware used in constructing wooden trusses which enhances the ease of installation and increases the resultant structural rigidity of the installed trusses for bearing structural loads.
2. Description of the Prior Art
In constructing various types of wooden truss assemblies, including both roof trusses and floor joists, it has been common to use large wooden structural members such as 2".times.10"s. Such large wooden members, however, are becoming increasingly difficult to obtain and have increased in cost substantially. Consequently various alternatives have been sought for enabling the construction of trusses which are able to bear the structural loads of full dimension lumber but which are constructed from smaller pieces of dimension lumber such as 2".times.4" members which are spaced apart by metal connectors. Substitutes for full dimension lumber roof trusses and floor joists must satisfy two primary criteria. First, the trusses must be able to withstand large compressive loads so that they may be used for bearing substantial structural loads. Secondly, it is desirable that the trusses be prefabricated at a manufacturing plant at a low labor cost and shipped to a building site without a high degree of risk of incurring damage to the trusses.
Various types of hardware have been developed for making prefabricated trusses. U.S. Pat. Nos. 3,025,577 to Jureit, 3,298,151 to Jureit and 4,078,352 to Knowles and the aforementioned U.S. Ser. No. 337,671 are representative of metal connectors which have been used for manufacturing trusses from dimension lumber such as 2".times.4"s.
The aforementioned U.S. patent application Ser. No. 337,671 entitled TRUSS STRUCTURES CONSTRUCTED WITH METAL WEB MEMBERS filed on Jan. 7, 1982 discloses a metal web member which has a reinforced leg having a projection which runs substantially the entire length of the leg and which projects in the direction of the sharp projections of connecting plates disposed at the ends of the leg. The height of the projection varies from a maximum in proximity to the connecting plates to a minimum in proximity to the midpoint between the connecting plates. A pair of flanges are joined to the outside edges of the leg along the length of the leg which flanges project in the direction of the sharp projections of the connecting plates. The height of the projection of the flanges varies from a minimum in proximity to the connecting plates to a maximum in proximity to the midpoint between the connecting plates. A pair of projections at each end of the legs may be used in place of the single projection which extends the length of the leg.
Attachment members have been marketed for connecting together the spaced apart wooden members which are used for constructing trusses. These attachment members have first and second connecting plates disposed at opposite ends of an intermediate section which extends transversely between the ends of the spaced apart first and second wooden member of the truss. The intermediate section of the aforementioned attachment members contains a plurality of ridges which project outward away from the direction that the sharp projections in the connecting plates project when engaging the spaced apart first and second wooden members of the truss.
Trusses have been installed at the building site in a number of ways. If the trusses are being used to construct a floor, they may be laid on top of the foundation walls and nailed into a beam which extends perpendicular to the longitudinal axis of the trusses. The trusses have been nailed in place by toenailing through various surfaces of the wood at the end of the truss.
It has been found that trusses of long length have the property of flexing to an undesirable extent if the center between the ends of the truss is not braced with a transverse beam when heavy structural loads are placed near the center. Thus, while it is the case that trusses manufactured at factory sites have eliminated the need for using expensive full dimension lumber, it is nevertheless the case that to some extent they have the property of undesirable flexation when they are used for long spands in supporting heavy structural loads.